Recently I mentioned a Baja California-brewed "Runaway IPA" whose label cheekily mocked the famous "immigrants crossing" sign on I-5 and other roads just north of the U.S.-Mexican border. A reader in Southern California says that the signs weren't really so preposterous:

I don't want to "harsh your mellow", as Charles Pierce is fond of saying, but having driven that stretch on and off (mostly on) for 15 years commuting to Santa Ana I've seen my share of people darting across the road, almost hitting one.  I also saw a man stretched out in the middle of the highway one night coming home from work who appeared dead when I passed by (he was already being attended to).  So yes, I laugh at the sign too but it was put there for a serious reason. 

Actually, once they built the fence down the middle median most of the pedestrian crossing attempts stopped.  I think the major reason for the crossings was when drivers, seeing the Border Patrol checkpoint open ahead, stopped to kick out their passengers. ...

That wasn't the only dangerous behavior I witnessed over the years.  Once getting off the Amtrak in Santa Ana, I saw two men standing on the outside ladder rungs between two cars.  This was during a period when the Border Patrol would board in Oceanside and check passengers as we headed north.

Offered for the record.

UPDATE Another reader writes in to say:
 I agree with your correspondent [above].  I did my grad work at Irvine in the late 80s and then lived in San Diego for a couple of years in the early 90s. I had a good friend in SD so I drove I-5 with some frequency.  At this point, I can't say how many deaths there were in that period, but certainly more than a few, and between he possibility for setting off a chain of accidents in reaction to people dashing out into traffic (which I certainly did see more than once) and the trauma of running someone over, even if it's not your fault, the warning was reasonable.
The image, on the other hand, is something I'd like to see explained.